Increasing numbers of motor vehicles have, for safety reasons, monitoring systems comprising pressure sensors mounted on each of the wheels of the vehicle and dedicated to measuring the pressure in the tires with which these wheels are equipped, and intended to inform the driver of any abnormal variation in the measured pressure.
These monitoring systems conventionally comprise:                mounted on each of the wheels of the vehicle, a box—termed wheel unit—incorporating in particular a sensor, a microprocessor electrically powered by a battery, and an emitter, for example of the radiofrequency emitter or inductive emitter type,        and, mounted on the vehicle, a central unit for receiving the signals emitted by the emitters, particularly provided with a computer incorporating a receiver, such as a radiofrequency receiver or an inductive receiver, connected to an aerial.        
Usually, and for each tire:                measurements of the pressure of the air in this tire are taken periodically by the associated pressure sensor,        then any variations ΔP in pressure between the values of the pressures successively measured are deduced from these measurements,        and, finally, when a variation ΔP in pressure between two measured pressure values is higher in terms of absolute value than a predetermined threshold Sp, the emission of a signal representing a variation in pressure to the central unit is commanded.        
The central unit for its part is programmed to process the signals emitted by the sensors in each wheel and, particularly after comparing and correlating said signals, to deliver a message able to inform the driver of an abnormal pressure variation in one of the wheels of the vehicle, and to identify the wheel concerned.
One of the disadvantages of such a design lies in the fact that all the variations in tire pressure higher than the predetermined threshold give rise to the emission of a signal to the central unit which alone, by virtue of its computational power and its ability to compare and correlate the signals received from the various sensors, is able to process the signals received in such a way as to determine whether they do actually represent a true anomaly in the tire inflation pressure.
Now, the processing performed by the central unit has revealed that a large proportion of the signals emitted to this unit are not representative of a true anomaly in the tire inflation pressure and these signals therefore have no justification in being emitted.
It is therefore apparent from this observation that a great many signals are needlessly emitted to the central unit by the wheel unit, thus shortening the battery life of the batteries used to power the microprocessors fitted on the wheels and needlessly and significantly “contaminating” the environment surrounding the vehicle, thus giving rise to increased risks of parasitic interference between nearby vehicles.